The present invention relates to an improved hydraulic oil tank that provides hydraulic oil to both the steering and brake cooling systems of a vehicle, such as a dump truck. In particular, the invention relates to a hydraulic tank that has two separate hydraulic oil environments, one for supplying steering oil and one for providing brake cooling oil, that share common oil.
Hydraulic systems for the steering and brake systems of a truck typically have either a totally common hydraulic tank that supplies both the steering and brake cooling oil to the steering and brake systems or two totally separate hydraulic tanks, one for the steering system and one for the brake cooling system.
Systems that employ a totally common hydraulic tank, however, risk having contaminants from the brake cooling oil enter the hydraulic steering system or circuit and cause a steering failure. Contamination of the brake cooling oil can result from brake wear or from a catastrophic brake failure. Some systems have hydraulic oil filters positioned in the hydraulic circuit between the brakes and the hydraulic tank for filtering contaminants from the brake cooling oil. However, these filters can become over saturated so that contaminated oil is able to bypass the filter.
Whereas the use of two totally separate hydraulic tanks can prevent contaminated brake cooling oil from entering the steering oil circuit and causing a steering failure, it can also be costly to implement. Furthermore, over time the volume of oil in the steering circuit may decrease due to leakage of oil across the brake seal, as explained in more detail further below.
Inside many typical disc brakes for trucks is a seal that separates the brake into brake application and brake cooling sections. Oil used in the brake application section for applying the brakes comes from the steering oil circuit and, in particular, from the steering accumulators which store oil at higher pressures. Due to the resulting pressure differential between the two sections when the brakes are applied, oil may leak from the brake application section to the brake cooling section across the brake seal. Over time this leakage can be significant and cause a decrease in the volume of oil in the steering oil circuit and an increase in the brake cooling oil circuit. If these two circuits are totally separated, as in the case where two totally separate hydraulic tanks are employed, then the oil that has leaked across the brake seal can not return to the steering oil circuit.
The present invention provides a single hydraulic tank which allows oil that has leaked across the brake seal from the brake application section to the brake cooling section to return to the steering circuit. While allowing "leaked" oil from the brake cooling section to return to the steering circuit, the present invention also prevents contaminants that may be present in the brake cooling oil from entering the steering circuit.